(a) Field of the Invention
The present invention relates to a method for preparing thermoplastic resin having weatherability, and more particularly to a method for preparing thermoplastic acrylate-styrene-acrylonitrile (ASA) resin having excellent weatherability and color matching properties.
(b) Description of the Related Art
Recently, as the thermoplastic resin industry has advanced and the distinctiveness of goods model has gained popularity, research on giving high function of colorability etc, to materials used in the industry has progressed a great deal.
In order to increase resin functionality, the prior art has used an acrylonitrile-butadine-styrene (ABS) copolymer resin. Although ABS resin has good qualities of impact resistance, processibility, and surface gloss, etc., it has a problem in that it is unsuitable for use outdoors due to bad weatherability and light resistance because of properties of the resin, and thermal stability is also bad, chemical resistance is weak, and its properties diminish over time.
In order to solve these problems, acrylate-styrene-acrylonitrile (ASA) resin is being developed.
In a method for preparing ASA resin of the prior art, Japanese Laid-Open Patent Publication No. Hei 5-202264 has suggested a method for improving properties by preparing ASA resin with a bimodal shape. The method discloses that ASA resin with a small diameter of 50xcx9c200 nm, and ASA resin with a large diameter of 200xcx9c1000 nm each prepares, and then the two resins are latex blended together, and resultant blends with a separately prepared styrene-acrylonitrile (SAN) copolymer to produce ASA resin having superior weatherability.
However, since the method separately prepares two ASA resins the process is complex, and colorability, surface gloss, and sufficient impact strength are not exhibited. German Patent No. 1260135 has described the method in detail.
In another method, Japanese Laid-Open Patent Publication No. Hei 4-180949 discloses a method for preparing ASA resin by making multi-layer graft copolymer particles. The method suggests a preparation of ASA resin for improving weatherability in which a hard core is first prepared by using a monomer having a high glass transition temperature, then a crosslinked acrylate rubber component is added, followed by a crosslinked shell of a styrene monomer, an acrylonitrile monomer having a high glass transition temperature, and a crosslinking agent, and finally by preparing a soft shell with an uncrosslinked styrene monomer and an acrylonitrile. However, this method also does not mention a method capable of improving colorability and surface gloss of ASA resin.
As explained, although a general ASA resin has weatherability, chemical resistance, and thermal stability, it has problems of a lowering colorability and surface gloss, weak side impact strength, and its molding capacity is limited due to a low fluidity. Additionally, important technical difficulties to overcome in the preparation of ASA resin are known to be that colorability and surface gloss showing a pearl color etc. while color matching are reduced, and impact strength is low. Also, color dispersion falls due to properties of acrylate rubber.
The present invention is made in consideration of the problems of the prior art, and it is an object of the present invention to provide a method for preparing thermoplastic acrylate-styrene-acrylonitrile (ASA) resin having superior weatherability, as well as properties and colorability equal to ABS resin.
It is another object of the present invention to provide a method for preparing thermoplastic resin having superior impact resistance, chemical resistance, and surface gloss.
In order to achieve these objects, the present invention provides a method for preparing a weatherable thermoplastic resin comprising the steps of:
a) preparing a seed by adding 0.05-0.2 weight parts of a water-soluble initiator to 0.5-10 weight parts of either an aromatic vinyl compound or a (meth)acrylic acid alkyl ester,
and polymerizing;
b) preparing an alkyl acrylate rubber polymer by adding
i) 5-45 weight parts of an alkyl acrylate monomer,
ii) 1-5 weight parts of an aromatic vinyl compound, a (meth)acrylic acid alkyl ester, or a vinyl cyanide compound,
iii) 0.2-1.0 weight parts of a metal salt derivative of alkyl sulfosuccinate with C12xcx9cC18, or a metal salt derivative of alkyl sulfuric acid ester, or metal salts of sulfonate, with C12xcx9cC20, as an emulsifier, and
iv) 0.05-2 weight parts of an oil-soluble initiator to the seed,
and polymerizing; and
c) preparing a thermoplastic resin by adding
i) 10-40 weight parts of an aromatic vinyl compound,
ii) 1-20 weight parts of a vinyl cyanide compound,
iii) 0.5-3.0 weight parts of metal salts of rosinate or metal salts of carboxylate, with C12xcx9cC20, as an emulsifier, and
iv) 0.05-0.2 weight parts of an oil-soluble initiator to the alkyl acrylate rubber polymer, and graft copolymerizing.
The present invention also provides a weatherable thermoplastic resin prepared by the above method.